1. Technical Field
The present invention relates to a lens module, a method for assembling the lens module and a camera module using the lens module.
2. Description of Related Art
With the ongoing development of microcircuitry and multimedia technology, camera modules such as still cameras and digital cameras are in widespread use or being combined with various electronic devices. Such camera modules are needed to satisfy requirements of compactness, low cost, and excellent optical performance.
A camera module of the related art includes at least one lens module and an image sensor module. The lens module is basically composed of a barrel, and lenses, spacers and an aperture received in the barrel. The image sensor module includes a holder and an image sensor received in the holder. The lens module and the image sensor module are preferably aligned with each other along an optical axis, i.e., concentrically aligned. A fixed focus camera module usually uses one lens module with a barrel thereof being threadedly engaged with a holder of an image sensor module. The barrel may be secured to a position in the holder by applying an adhesive, or movable relative to the holder under a driving device to achieve a focusing function. A zooming camera module usually uses two or more lens modules, the barrels may be driven by motors to move relative to each other as well as the image sensor, thereby achieving a zooming function.
However, the fixed focus camera module or the zooming camera module mentioned above does not take lens optical tolerance into consideration. The smaller the optical tolerance is, the greater influence of decentration on the lens optical performance will be. Thereby, during assembly, focusing or zooming of the lens module, the movement of the lens with smaller optical tolerance will easily lead to loss of concentricity and reducing image quality.
What is needed, therefore, is a lens module which takes optical tolerance into consideration and a method for assembling the lens module.
What is also needed is a camera module using the lens module.